Time-element device.



N. WILKINSON.

TIME ELEMENT DEVICE.

APPLLGATION FILED APR.17, 1911.

1, 1 1 8,608. PatenteiNov. 24, 1914.

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UNITED STATES PATENT orrron.

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Application filed April 17, 1911. Serial No. 621,665.

To a ll-io homl-it may concern:

Be it known that I, Nam WILKINSON, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and.

State of Wisconsin, have invented certain new and useful Improvements in Time-Element Devices, of which the following is a full, clear, and exact specification.

My'f invention relates to thermostats, particularl in connection with time-element circuitreakiug devices.

In the ordinary construction of thermostats, the two elements, formed of different metals, have usually been riveted together, one end of the composite strip being fixed while the other is free to move to accomplish the desired result. This produces a very flimsy structure, the composite strip being easily bent. Moreover, the deflection of such a composite strip is caused merely by the dilferential expansion of the strips upon equal heating. When thermostats have been used in connection with electric switches, the thermostat operating or forming the movable element of the switch, the operation of such switch has been exceedingly slow, thus making arcing at the contacts of the switch practically inevitable.

It is the object of my present invention toavoid these difficulties. This is accomplished by making the thermostat in a truss form, the two strips of the thermostat and their commonbase preferably formin a The resultant structure is m and substantial, is of easy and permanent adjustment, and is not easily damaged. Moreover, it allows the heating of one of the elements'of the thermostat without the other, as by an electric heating coil wrapped uponone strip of the thermostat only; thus the deflection is not dependent upon different co-efficients of expansion of the materials forming the two strips, which may be made of the same material. This thermostat is combined with mechanism for obtain ing a snap action of a-switch' operated by the thermostat.

The variousnovel features of my'invention will appear from the description and drawings, and will be particularly pointed out in the claims.

Figure 1 shows a thermostat embodying my invention, as applied to an overload and no-voltage circuit-breaker, the switch actuated by the thermostat being in closed positiori; and, Fig. 2 shows the same thermostat just after it has tripped its switch.

The thermostat proper consists of two metal strips or-rods 10 and 11. The stri 10 is preferably made .of a brass tube wit the ends flattened, while the strip 11 is made of a flat steel spring. However, the strips may be made ofany desired material, and are not necessarily of unlike material. The left hand ends of the strips 10 and 11 are mounted in common on a post 12, being spaced apart by a thickwasher 13 and heldginplace.

by ascrew 14. Their right hand ends are fastened firmly together in any desired manner, as by rivets or solder, or by a screw 15, the latter also servmg as an'adjusting' screw which may be locked in position by a book 16 formed by an extension of the spring strip 11. wound with a heating coil 17, one end of which is connected to a contact'terminal 18 and the other, by way of a shunt'20, to the movable spring contact 19 of a switch. The

movable contact 19 .is mounted on a bellcrank lever 21, and cooperates with afixed contact 22 at the bottom of a contact terminal23, the two contact terminals 18% and 23 being normally bridged by a member-'24 which may belifted out of engagement with one or both by an overload coil 25. The bridging meinber'24 thus short-circuits the heating coil 17 and the switch 19. Pivoted to the lower end of the vertical arm of the bell-"crank lever 21 is a second bell crank Y lever 26, the long horizontal arm ofwhich extends above and substantially parallel to the strip 11 and may be engaged near its fulcrum by the adjusting screw 15..' The bell-crank levers 21 and 26 are biased in clockwise and counter-clockwise directions respectively by a spring 27, but are normally held from movement in such directions by the weight of the-bridging member 24: resting on the screw 28 carried by the horizontal arm of the bell-crank lever 21, and by'a stop 29 with which a notch at the end of the horizontal arm of the bell-crank lever 26 engages. v In H The thermostat and switch above described are shown as controlling a circuit-breaker 30, arranged in the mains 31 of an electrical dis tribution system of; any desired type. The circuit-breaker is biase to open position,but may be held closed by the no-voltage coil 32, the circuit of which includes the contact ter- The'strip or tube 10 is mluals l8 and 23 and some connection befor the circuit of the no-voltage coil 32 to pass through the heating coil 17 and the switch contacts 19 and 22.

causin it to expand longitudinally and raise t 1e right hand or joined ends of the strips 10 and 11. The coil 17 has little or no heating efi'ect on the strip 11. If the overload is but momentary, the overload coil 25 allows the bridging member 24 to drop to short-circuit the heating coil 17 and the switch contacts 1 9 and 22. If the overload continues, however, the expansion of the tube 10 under 20 the influence of-the heating coil 1'3 continues until the screw 15 has lifted the left hand end of the horizontal arm of the bell-crank lever 26 clear of the stop 29, whereupon the spring 2? immediately contracts and moves theparts 26, 21, and 19 to the left, to the position shown in Fig. 2. This separates the switch contacts 19 and 22, thus breaking the circuit of the no-voltage coil 32 md tripping the circuit-breaker 30. Upon the opening 32' of the circuit-breaker and the consequent denergization of the overload magnet 25,

the bridging member 2% drops and forces the screw 28 downward, thus moving thecontact 19 again into engagement with the 33* contact 22, and the bell-crank-lev'er 26 at least far enough to the right to allow the notch at its end to engage the stop 29. Since it takes some little time for the strip 10 to cool and contract to its former length, such 48 notch does not immediately engage the stop 29. Thus if the circuit-breaker 30 is immediately re-closed it will immediately be re tripped if the overload still continues, for the lifting of the bridging member 2% by the magnet 25 allows the immediate separation of the contacts 19 and 22 and the immediate interruption of'the circuit of the no-voltage magnet 32. However, if the circuit-breaker is not immediately re-closed, or i it is re- 5i) closed but the overload has ceased, the bridging member 24 will remain down, and hold the contacts 19 and 22 in engagement until by the cooling and contraction of the strip 10 the notch in the end of the bell-crank lever 26 has again engaged the stop 29. Ifan overload then occurs, the circuit-breaker 30 The coil 17 im- 10 mediately begins to heat the strip or tube 10,.

switch in another position, l;=eing normally free from and will be tripped only after an interval of time, in the manner above described. This interval of time may be adjusted with great accuracy by the screw 15.

The thermostat above described, whether with or without the heating coil 17 and the switch contacts 19 and 22, may bensed for any purpose for which any thermostat may be used. Its construction, as well as that of the parts associated with it, may lJB'JllOdlfiGd widely, and in the following claims'l aim to cover all such modifications which come within the spirit and scope of my invention as defined in the following claims.

What I claim as new is:

1. A thermostat, comprising two members fixed and spaced apart atone end and joined together at the other end, and an adjustable part extending through said members at their joined ends, a portion of one of said members being resilient and engaging said adjustable part to form a lock therefor.

2. In combination, a support, a thermostatic element mounted on said support, a switch, aresilient member attached to said support for biasing said switch to one position, and latching means for holding said said thermostat adapted to engage and trip said latch.

3. lncombination, a, switch biased to one position, 'a l'atch for holding said switch in another position, a thermostat comprising two members spaced apart'at one end and secured together at the other end, and an adjustable element at the latter end for tripping said latch.

5 in combination, a switch, means for biasing said switch to one position, a latch for'holdin'g said switch in another position, said switch-biasing means biasing said latch to switch holding position, and a thermostat for tripping said latch.

5. In combination, a switch, a latch for holding said switch in one position, means for biasing said switch to another position, said switch hi means being ellective to bias said latch toward one position, and a thermostat for tripping said latch.

in testimony whereof I afilx my signature, in the presence or" two witnesse NATHAN a" roar SON.

Witnesses G. B'Somnr, r: L BYRON. 

